Rubber heel



May 30, 1961 J. D. BORROFF ET AL 2,985,972

RUBBER HEEL Original Filed March 26, 1958 2 SheetsSheet 1 FIG. I

FIG. 2

FIG. 3

INVENTORS JOHN D. BORROFF 8. BY OY REYNOLDS ATTORNEY I/KQEQQQQ May 30, 1961 J. D. BORROFF ET AL 2,985,972

RUBBER HEEL Original Filed March 26, 1958 2 Sheets-Sheet 2 3| 3 45 28 W K INVENTORS 1 JOHN D. BORROFF a I COY REYNOLDS 9 "f r 12; M 3 7 30 FIGS ((7 ATTORNEY United States Patent RUBBER HEEL Original application Mar. 26, 1958, Ser. No. 724,163. and this application May 24, 1960, Ser. No.

2 Claims. (Cl. 36-65) This invention relates to an improved rubber heel. The term heel is used herein to refer to that part of a shoe heel which forms the walking surface and includes whole heels, half heels, etc.

The attaching surface of the heel of this invention is provided with an outwardly, upwardly slope edge portion which extends from a position adjacent the front (or breast) edge at one side of the heel to a position adjacent the breast edge at the other side of the heel. Adjacent the inner edge of said sloping edge portion is a groove which likewise extends continuously from a position adjacent the breast edge at one side of the heel to a position adjacent the breast edge at the other side of the heel. This groove is preferably located immediately inwardly from the inner edge of said sloping edge portion or is in said sloping edge'portion itself, and is substantially coextensive therewith. When a heel with such a sloping edge portion and such a groove in its attaching surface is nailed to a shoe, the attaching surface flexes outwardly from the groove, making firm and intimate contact with the surface to which it is attached. Thus, the heel conforms more readily to irregularities in the surface than if the heel had been provided with a sloping edge portion only, without a groove.

The heel of this invention may contain washers for guiding or holding nails used to attach the heel to a shoe base, or it may employ a core for this purpose. Such cores are relatively stiff. The edge of a heel with such a sloping edge portion and a core adjacent its inner edge flexes outwardly more uniformly if it contains a core, than if it contains washers because the stiffness of the core causes the whole area of the heel where it is located to move as a unit when the heel is nailed to the shoe base. This is not the case with a similar heel containing washers. When a heel with such a sloping edge portion and a groove adjacent the inner edge of the sloping portion is fastened to a heel base, a tighter edge is obtained if the heel contains a core than if it contains washers.

Rubber heels are usually cured in multiple-cavity molds. For example, each mold may contain sixty cavities. The difficulty with employing plastic cores has been that normally it takes several minutes for the operator to prepare --all of the cavities in a single mold. The molds are not cooled appreciably between heats, and many cores melt or soften in the mold and flow away from their original location before the rubber is vulcanized. In the description which follows, the heel of this invention will be described as prepared in a mold cavity provided with means to hold a plastic core out of contact with the mold cavity until after rubber has been placed in the mold cavity and the mold is closed. However, it is to be understood that it is not necessary that the heel be made in this way, nor is it necessary that the heel contain a core.

. The depression or groove in the attaching face of the heel near the inner edge of the sloping edge portion is Patented May 30, 1961 2 formed by a dam. This dam is continuous from a location adjacent the breast wall at one side of the cavity to a location adjacent the breast wall on the opposite side of the cavity. Generally, both ends of the dam are spaced a short distance from the breast wall. There may be no sloping portion along the breast edge of the heel, and there is no dam across the breast wall of the mold.

The invention will be further described in connection with the accompanying drawings, in which- Fig. 1 is a section on the line 1--1 of Fig. 2, of a partially closed heel mold being closed between platens, with a biscuit of rubber in the mold and a core supported on P Fig. 2 is a plan view of this mold with the face plate removed;

Fig. 3 is a sectional view of the same mold after the mold is closed;

Fig. 4 is a section through the finished heel;

Fig. 5 is a view in the walking surface or tread of the finished heel;

Fig. 6 is a view in perspective of the finished heel, showing its back, sometimes referred to herein as the attaching surface;

Fig. 7 is a rear view on the line 7-7 of Fig. 8, of a,

shoe with the heel of Figs. 4 to 6 fastened thereto; and with a portion of the heel broken away; and

Fig. 8 is a side view of the rear portion of the same shoe with the heel shown in section.

A heel mold is usually formed of a face plate 1, a back plate 2, and a middle plate 3. To form a heel, the mold is placed on the lower platen 5 of the press before therubber has been pressed into the mold so as to fill it, and the face plate 1 rests on the portion of the rubber which has not yet been forced into the mold. The mold is then closed by applying pressure to one or. both of the platens 5 and 6, as illustrated in Fig. 1.

In forming the heel, a plastic core 10 is put in each cavity, and rubber 11 is supplied to the mold. This rubber may be in the form of a biscuit, as illustrated in Fig.

l, or it may be supplied to the mold in any other form.

The mold of Fig. 1 shows pins 13 fitted in openings 14 in the back plate. When a core is placed on the pins, it is supported out of contact with the back plate of the hot mold until it is forced to the back plate of the mold by the pressure of the rubber against it when the mold is closed.' When rubber has been placed in the mold and the face plate is lowered by bringing the two platens toward one another, the core is forced down around thev pins into contact with the heated back plate of the mold.

Almost simultaneously therewith the rubber 11 is forced down over and around the core, surrounding it. If the core is melted .by contact with the hot back plate of the mold, or softened so that it will flow under pressure, it

can flow very little, because almost at the same time as I it contacts the heated mold it is surrounded with rubber which restricts its flow. The dam 35 minimizes such'fiow in an outward direction except toward the breast edge of the heel where there is no dam. a

Figure 1 shows the piston ram 20 being lowered so that the biscuit will be under pressure and the core will be pushed to the back plate of the mold as the rubber of the biscuit flows and fills the mold cavity. The plastic melts and forms a strong bond with the rubber. The mold cavity is surrounded by the overflow groove 22 into which excess rubber flows as the press is closed.

The mold of Fig. 1 includes a central boss 25 which L projects up through the opening in the center of the core the heated core plastic. It is conceivable that instead of being supported on pins, the core may be supported on the boss out of contact with the back plate and other surfaces of the hot mold before introducing the rubber into the mold.

As shown, the heel is molded upside down--that is, the surface 30 of the heel which contacts the face plate (Fig. 3) during the molding and curing of the heel is the walking-face 30 of the heel (Figs. 4"and-5) when it is applied to a shoe. Conversely, the back 31 of the finished heel (Figs. 4 and 6) is the attaching surface 31 which is formed against the back plate of the mold.

The core receives the nails used to hold the heel to a shoe, and is located at or near the attaching surface of the heel, i.e. the surface which contacts the shoe. As shown in Fig. 1, it is placed in the mold cavity before the rubber is put into the cavity, and the rubber presses it against the back plate of the mold as it is pressed down against it and around it. In this way, the core is located inside of the dam 35 and any tendency to flow beyond the dam is greatly restricted. A slight overflow is not objectionable. The boss positively locates the core in the heel away from the breats edge 37. Even though the plastic of the core were to flow outwardly to the breats wall 38 of the mold, it would do little damage, as it is scarcely noticeable at this location. Because of the differance in the texture of the core plastic and the rubber, any plastic that is exposed on the wall 39 of the heel (Figs. 4-6) by flowing outwardly to the wall 40 (Fig. 2) of the mold disfigures this wall of the heel and makes trimming more diflicult. Also, because the plastic is stiff it reduces or even destroys the contour-compensating factor of the flexible edge of the heel.

In the mold shown in Figs. 1-3 the outer edge of the back plate of the mold, except across the breast of the cavity slants downwardly and outwardly at 42 to produce the sloping portion 43 (Figs. 4 and 6) around the edge of the heel. The dam 35 forms the depression 45 at the inner edge of this sloping portion. This causes the entire edge portion to flex outwardly when .the heel is nailed to a shoe, as shown more particularly in Figs. 7 and 8. As the heel is drawn to the shoe by nailing, the 'wall 39 which is perpendicular before nailing (Figs. 4 and 6) becomes flared at the back surface as the depression is forced to spread by the pressure of the sloping edge portion against the bottom of the shoe. Figures 7 and 8 show this flaring on heels before trimming. The extra flexibility of the edge portion because of the depression 45 allows the heel to conform more readily to irregularities in the surface to which it is attached.

Pins 13 form depressions 47 (Figs. 4, 6, 7 and 8) in the finished heel.

The dam of this invention is located on the back plate of the mold and forms a depression in the back of the heel. The depression formed by the dam is on the back surface of the heel and does not affect the ultimate appearance of the heel, because it is not exposed to view after the heel is applied to a shoe. As the heel is applied to the shoe, the depression permits relative movement of the different areas of the back surface of the heel on the opposite sides of the depression, and this is an advantage which is accentuated when the heel is formed with a sloping edge portion.

Theplastic of which the core is formed may be thermoplastic or thermosetting or a mixture of the two. It may, for example, be composed essentially of any of the following: butadiene-styrene resin, butadiene-acrylonitrile resin, and tri-polymers such as those produced from butadiene, styrene and acrylonitrile; polyvinyl chloride and copolymers of vinyl chloride and other monomers; mixtures of any one of the resins with one ormore rubbers such as butadiene-acrylonitrile rubber; mixtures of butadienestyrene rubber or butadiene-acylonitrile rubber and moditied phenol-formaldehyde plastics; urethane-type polymers etc. A satisfactory formula is:

Parts by weight Butadiene-styrene rubber 1 25 Styrene-butadiene resin 75 Precipitated calcium carbonate 40 Zinc oxid 5 Stean'c d 1 Benzothiazyl rlisnlfirle 1.5 Tetramethylthiuram monosulfide 0.15 Sulfur 2 1 Emulsion-polymerized from 75 parts of butadiene and 25 parts of styrene.

z Emulsion-polymerized from parts of styrene and 15 parts of butadiene.

The plastic compositions mentioned are illustrative and the invention is not limited thereto. Neither is the invention limited to the types or shapes of heels or molds illustrated. The cores may be of different shapes and designs, and the heels may be of different shapes and designs. The dams may or may not be a permanent part of the mold.

The term rubber is used herein to include natural rubber and synthetic elastomers which in the cured state have suflicient resilience for use in rubber heels. The terms soften and softenable are used in the claim to include melt and meltable. The term nail and variations thereof are used to include staples and the like.

This application is a division of our application Serial No. 724,163, filed March 26, 1958.

The invention is covered in the claims which follow.

What we claim is:

1. An improved rubber heel, the attaching surface of which has an outwardly, upwardly sloping edge portion along the sides and back of the heel, which is continuous from a position adjacent the breast edge at one side of the heel to a position adjacent the breast edge at the opposite side of the heel, and a continuous groove in said surface of the heel adjacent the inner edge of said sloping edge portion, the portion of the heel outside of the groove being thereby adapted to flex outwardly from said groove when the attaching surface of the heel is pressed against a flat surface, the improvement according to which the attaching surface of the heel is continuous from the breast edge to the central portion of the heel so that the portion of the heel along the entire breast edge is incapable of flexing outwardly away from the balance of the heel.

2. An improved rubber heel, the attaching surface of which has an outwardly, upwardly sloping edge portion along the sides and back of the heel, which is continuous from a position adjacent the breast edge at one side of the heel to a position adjacent the breast edge at the opposite side of the heel, there being a core in the central portion of the heel to retain nails used to nail the heel to a heel base, which core stiflens the area of the heel in which it is located, and a continuous groove in said surface of the heel adjacent the inner edge of said sloping edge portion, the portion of the heel outside of the groove being thereby adapted to flex outwardly from said groove when the attaching surface of the heel is pressed against a flat surface, the improvement according to which the attaching surface of the heel is continuous from the breast edge to the central portion of the heel so that the portion of the heel along the entire breast edge is incapable of flexing outwardly away from the balance of the heel.

References Cited in the file of this patent UNITED STATES PATENTS 1,482,457 Bigoney Feb. 5, 1924 1,587,442 Teetsal June 1, 1926 1,610,319 Ray Dec. 14, 1926 1,681,217 Bunker Aug. 21, 1928 1,686,397 Roberts Oct. 2, 1928 1,698,791 Hadaway Ian. 15, 1929 1,738,048 Goodwin Dec. 3, 1929 1,877,298 Goodwin Sept. 13, 1932 2,090,244 Waters et a1. Aug. 17, 1937 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 2,985,972 May 30, 1961 I John B-orroff et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 20, for "slope" read sloping column 2 line 69, for "walking'" read attaching column 3, lines 23 and 24, for .breats", both occurrences read breast column 4, in each footnote following the table, the dash should be a hyphen lines 30 and 4L5 for "An improved" each occurrence read In a Signed and sealed this 28th day of November 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

